local json = require "json"
local databaseStorage = peripheral.find("drive") or error("No drive attached", 0)
if (databaseStorage.isDiskPresent() == false or databaseStorage.getDiskLabel() ~= "Farming Data") then error("Missing or wrong drive", 0) end

local databaseModem = peripheral.find("modem") or error("No modem attached", 0)
local fieldDataChannel = 420 -- Request Field Data Channel
local setupFieldChannel = 421 -- Setup Field Channel
if (databaseModem.isOpen(fieldDataChannel) or databaseModem.isOpen(setupFieldChannel)) then databaseModem.closeAll() end
databaseModem.open(fieldDataChannel)
databaseModem.open(setupFieldChannel)

local function listenForFieldDataRequests() 
    while true do
        local event, _, incomingChannel, replyChannel, message, _ = os.pullEvent("modem_message")
        if (incomingChannel == fieldDataChannel) then
            local databaseFile = io.open("/" .. databaseStorage.getMountPath() .. "/field_data.txt", "r")
            local database = json.decode(databaseFile:read("*a"))


            databaseFile:close()
            databaseFile = nil
        end
    end
end

local function listenForFieldSetups() 
    while true do
        local event, _, incomingChannel, replyChannel, message, _ = os.pullEvent("modem_message")
        if (incomingChannel == setupFieldChannel) then
            local databaseFile = io.open("/" .. databaseStorage.getMountPath() .. "/field_data.txt", "w")
            local database = json.decode(databaseFile:read("*a"))


            databaseFile:write(json.encode(database))
            databaseFile:close()
            databaseFile = nil
        end
    end
end

local function listenForDiskEject() 
    repeat
        local _, side = os.pullEvent("disk_eject")
    until side ~= nil
    error("Disk was ejected!")
end

local function listenForPeripheralDetach() 
    repeat
        local _, side = os.pullEvent("peripheral_detach")
    until side ~= nil
    error("Modem was removed!")
end

parallel.waitForAny(listenForFieldDataRequests, listenForFieldSetups, listenForDiskEject, listenForPeripheralDetach)